As is well known, in recent years, polyacetal resin has been utilized in a very wide field as an engineering resin due to its excellent physical characteristics such as its mechanical and electrical properties chemical characteristics such as its chemical and heat resistance properties. However, expansion of the field in which the polyacetal resin is utilized is sometimes accompanied with further requirements of specific material property changes. Further improvement in weather (light) resistance is desired as one of such specific properties. That is, the environment in which the interior and exterior parts for automobiles and the parts for electric appliances are used (e.g., sun light, humidity due to rain and dew and aerial contaminants causes discoloration of molded product surfaces and gloss reduction attributable to loss of a surface flatness. In addition, such an environment generates cracks on the surfaces of such parts thereby causing in some cases damaged appearances.
This necessitates the use of a composition blended with various anti-weather stabilizers when the polyacetal resin is used for parts exposed to sun light. Various blends of anti-weather stabilizers are known. For example, there are proposed combined use of a hindered amine series light stabilizer and various UV absorbers (JP-A-57-98545, JP-A-59-133245, JP-A-60-195155 and JP-A-61-36339) and combined use of various UV absorbers, aliphatic ester and a hindered amine series light stabilizer (JP-A-61-47744).
However, the methods with these stabilizers can not necessarily be satisfied, and in order to maintain a weather (light) resistance over a long period of time, a large number of such stabilizers must be added. Since polyacetal resin is a high crystalline polymer, the additives tend to "bleed" onto the surface of the molded parts due to recrystallization caused by heat and temperature differences in the ambient environment. This in turn, causes discoloration and gloss reduction on the molded product surfaces which appears to be the same action as resin deterioration. In particular, the surface appearance of automobile interior parts which are used in very high temperature or high humidity environments may become damaged in spite of the part being formed of a polyacetal resin with improved heat resistance.
Accordingly, there is a need for to be developed between "material" and "which" a polyacetal resin material which is free of additive surface bleeding and maintains a molded product appearance over a prolonged time periods, while also maintaining weather (light) resistance properties.